Abstract The purpose of this proposed five-year MERIT project extension is to continue a longitudinal, controlled study of a universal, multicomponent intervention initially implemented with rural youth and families. The proposed plan is to follow our sample during late emerging adulthood, a phase critically important to the establishment of enduring patterns of substance use and substance-related problems affecting healthy adult functioning. The MERIT project research to date has addressed several key methodological problems typical in community-based preventive intervention research-in part, through the use of multimethod, multi-informant measurement procedures. Intervention and measurement demands of the study notwithstanding, the targeted schools (N = 36) were successfully recruited from a randomly selected set of schools and randomly assigned to a multicomponent family- and school-based intervention, a school-based intervention alone, and control conditions; all schools were retained through the 12th grade data collection point. Observation-based assessment confirmed high fidelity implementation of both family and school intervention components. Eighty- six percent of the pretest sample remained through the last wave of data analyzed post high school; there has been no loss of sample size in the post high school sample. The study also has addressed major gaps in the knowledge base on long-term effects of multicomponent family and school-based interventions in understudied populations; substantial progress has been achieved on all of the specific research aims in the original proposal. Notably, positive long-term substance initiation outcomes have been demonstrated through early emerging adulthood, with stronger effects among higher-risk participants and empirical verification of mediated effects through a protective shield of reduced substance use opportunities, along with evidence of economic benefits. A key indicator of initial progress overall is the completion of 46 manuscripts, among a total of over 150 manuscripts produced since 1993 through the larger program of research of which it is a part. The proposed study will evaluate long-term effects of a universal, multicomponent middle school intervention on participants in the late emerging adulthood phase; specifically, effects on substance use and related adult functioning (criminal and antisocial behavior, mental health, physical health, relationship quality and sexual behavior-Aim 1). In addition, it will examine mediating mechanisms of long-term multicomponent intervention effects on emerging adult substance use and related adult functioning, replicating and extending models empirically supported by earlier research (Aim 2). Finally, the project also will examine moderation of long-term intervention effects associated with early adolescent risk and the alteration of problem behavior trajectories associated with attending college and other life course changes (Aim 3).